Question 1

Which experiment provided the first evidence for the existence of electrons as negatively charged particles within atoms?

Accepted Answer

Thomson's cathode ray tube experiment

Question 2

In Millikan's oil drop experiment, the charge of the electron was determined by balancing the gravitational force and the electric force on oil droplets. Which equation represents the balance of forces used in this experiment?

Accepted Answer

$$F_{gravity} = F_{electric}$$

Question 3

Which of the following statements best describes the outcome of Rutherford's gold foil experiment?

Accepted Answer

Most alpha particles passed through the foil, but some were deflected at large angles, suggesting a small, dense nucleus.

Question 4

Which particle discovered by Goldstein is responsible for the positive charge in the nucleus of an atom?

Accepted Answer

Proton

Question 5

Which of the following types of radioactivity consists of high-energy electromagnetic waves and does not change the atomic number or mass number of the emitting nucleus?

Accepted Answer

Gamma decay

Question 6

An atom of carbon-14 ($$^{14}C) $$undergoes beta decay. What is the resulting element and its atomic number?

Accepted Answer

Nitrogen, atomic number 7

Question 7

Which equation correctly represents the relationship between the number of protons ($$Z$$), neutrons ($$N$$), and mass number ($$A) in an $$atom?

Accepted Answer

$$A = Z + N$$

Question 8

Which of the following best describes the Bohr model of the atom?

Accepted Answer

Electrons orbit the nucleus in fixed energy levels (shells).

Question 9

Which term refers to the smallest discrete quantity of energy that can be absorbed or emitted by an atom?

Accepted Answer

Quantum

Question 10

Which electron configuration represents a neutral sodium atom ($$Z = 11$$)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^1$$

Question 11

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes have the same number of protons but different numbers of neutrons.

Question 12

Which element is located in Group 1 of the periodic table and is highly reactive with water?

Accepted Answer

Sodium

Question 13

A radioactive isotope emits an alpha particle. What happens to its atomic number and mass number?

Accepted Answer

Atomic number decreases by 2, mass number decreases by 4

Question 14

Which of the following best explains why elements in the same group of the periodic table have similar chemical properties?

Accepted Answer

They have the same number of valence electrons.

Question 15

Which equation represents the energy of a photon emitted when an electron transitions between energy levels in the Bohr model?

Accepted Answer

$$E = h
u$$

Question 16

Which of the following is NOT a subatomic particle found in the nucleus of an atom?

Accepted Answer

Electron

Question 17

A sample contains two isotopes of chlorine: $$^{35}Cl$$ and $$^{37}Cl. If $$the atomic number of chlorine is 17, how many neutrons are in $$^{37}Cl$$?

Accepted Answer

20

Question 18

Which of the following best describes the relationship between electron configuration and an element’s position in the periodic table?

Accepted Answer

The electron configuration determines the group and period of the element.

Question 19

Which of the following is a real-world application of radioactivity?

Accepted Answer

Using radioactive isotopes in medical imaging (e.g., PET scans)

Question 20

Which of the following best describes the electrical properties of an atom?

Accepted Answer

Atoms are electrically neutral because the number of protons equals the number of electrons.

Atomic Structure and the Periodic Table: Key Concepts and Experiments

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